Six fights into his pro boxing career, Joey Spencer has yet to go past the second round.

The teenage fighter from Linden raised his record to 6-0 Sunday by recording his sixth straight knockout after stopping Brandon Harder of Mississippi in a super welterweight bout at the Microsoft Theater in Los Angeles.

Spencer, 18, sent the 39-year-old Harder (2-2, 0 KOs) to the canvas once in the first round and twice in the second before the referee stopped the bout at 1:27. The fight was scheduled for four rounds.

The quick KO led former world lightweight champion Ray "Boom Boom" Mancini, who was serving as a television analyst for the bout, to call for Spencer to face stronger opponents in the future.

“I’d like to see him step up now in opposition,” Mancini said. "This kid can fight. He’s only fighting four rounders. Move him up to six and fight better opposition. He’s fighting a lot of guys who have been older -- a lot older, not just a little older. Let’s start getting some guys who are closer to his age. Let’s see what he can do.

“Obviously Joey can fight. He can punch, he’s a strong kid but this fight told us nothing. I want to see him step up. He’s been Prospect of the Year voted by the fans last year. He can fight. Let’s turn him loose.”

Indeed, Spencer was voted Premier Boxing Champions' Prospect of the Year after going 5-0 in 2018.

Flint’s Anthony Dirrell, who was also serving as an analyst for the fight vs. Harder, agreed with Mancini.

“He definitely has to step his game up,” said Dirrell, who is good friends with Spencer. “You’re only as good as your opponent. He’s got to step his game up and really test him and see where he’s at, even from a mental standpoint.”

Spencer cut Harder on the head with an accidental headbutt in the first round, which ended with Harder taking a knee that was ruled a knockdown. Harder went down two more times in the second before the fight was stopped.

Spencer landed 34 of 77 punches. That included 24 of 47 power punches. Harder, on the other hand, landed just two of the 11 punches he threw and one of six power punches.

Spencer said he plans to fight four more times this year and that the plan is to for his next bout to be scheduled for six rounds.

He admitted he hasn’t faced the toughest fighters in the super welterweight division but is confident he’ll be ready when he gets in the ring with better opponents.

"You're going to get more and more tests in my career as I go," Spencer said during a post-fight interview in the ring. "I believe that I'll rise to the level of my competition. Sometimes you're going to go against an awkward guy and you'll be more uncomfortable than you would against a seasoned guy.

“When I get in there with a test, I know that I’m going to rise to that.”